Low cost, robust and efficient implementation of MPPT based buck-boost converter for off-grid PV applications

Rapidly growing solar PV energy sector demands development of low cost, reliable and energy efficient systems to continue its growth globally. Most PV systems deployed in the developed countries are based on grid-tied topology as the grid in these countries is largely stable. However, most of the developing world has an intermittent grid or a bulk of the population is not connected to the grid in the first place. In this context, this paper proposes a design and implementation of a low cost, efficient and robust maximum power point tracking based charge controller suited for stand-alone or backup PV applications. The charge controller incorporates a buck-boost topology that ensures a continuous battery charging in various conditions. The implementation includes a hardware protection against breakdown of converter switches in addition to a software based protection approach derived from converter analysis. The software algorithm, all programmed into a low cost 8 bit microcontroller, also incorporates a three state charging capability to charge battery under optimal conditions. The designed system was tested at 150W (output power) and performed optimally.